There was a truck website (for old suburbans I think) that had copies of literature related to the Warner R7 and R11 overdrives, but I can't find it at the moment.

The "other" Overdrive unit commonly available then was the Laycock design; which was used in a lot of British cars (MG's etc). Then I believe AMC bought a large pile of them, and some of those ended up being modified for the first Gear Vendors units which we still see today.